I'd only worry about drafts in cool weather. In summer, they need air flow. If you put a box fan in a window to blow outward, that draws hot air out and doesn't stir up alot of dust in the coop. Yes, ventilation is up high so it doesn't blow air across them on the roost in the winter. Think of drafts as lower and cold and ventilation as higher up to keep air moving through the coop.

Last year while building our hen house, our two hens refused to voluntarily sleep in the tractor's 'box'. It was just a box with straw in the bottom. It didn't have any roost bars. At this point, I would call the box a 'laying box', not a place for hens to sleep.

They would free range in the day and at night roost in a tree. Each night, we would get a ladder out, climb up in a tree, catch the sleeping birds and put them in the tractor.

Obviously, they didn't care about the wind. It is my understanding that wild chickens roost in trees. If so, what could their problem with 'drafts' be?

Also, this winter our hen lived outside in her unheated hen house. It got down to the teens on a couple of nights, but there were no problems.

Thus, we haven't seen a problem with 'wind', nor with 'cold' (at least down to 15 degrees F).

As best I can tell, the issue with drafts is 'temperature fluctuations.' If there is a heater in the hen house, and if there is also a cold breeze blowing through cracks in the walls, chicks/chickens some distance from the heater may experience fairly rapid fluctuations in temperature as alternating warm and cold air blow past. These may produce 'chills' and things go down hill from there when that happens.

If you put a box fan in a window to blow outward, that draws hot air out and doesn't stir up alot of dust in the coop.

It is not the wind on them. It is the wind in the coop that stirs up dust that they have trouble with, their respiratory system suffers when dust is kicked up and gets in thier tiny lungs.

Outside the air is fresh and the "drafts" don't bother them. So maybe your hens like it outside in the trees because it is dusty (I am not saying dirty) in their coop. Dust comes from the litter we use.

When I look up the definition of a draft, it says that a draft is 'admitting currents of air, usually uncomfortable' (from dictionary.com)

Ventilation is 'replacing stale air with fresh air.'

... so how to comfortably exchange stale air with fresh air is the question. I think it has to be a hard question when you are usually dealing with a single room box-type coop, and any incoming air is not climate controlled.

In winter, any in coming air into my coop is going to be cold. I don't know how to do that any other way... I guess the trick is to limit the air exchange such that the birds can maintain a comfortable overnight temperature while still getting fresh air?

Living in NW Alaska, I am not concerned about air exchange, especially with the high winds and daily wind all year round. There IS a lot of dust, its from the bedding, the poop and the feathers. Any person with parakeets in their house will tell you birds are messy and dusty. The draft thing is easy: When the hens fluff up to sleep, or any bird for that matter, the pockets of air between the feathers stays at a constant temp unless drafts or wind blow that warmth away and then there is a struggle to be comfortable and with loss of heat, energy expenditure while trying to rest, the need for more fuel aka feed to produce the energy to keep the body within a comfortable range of warmth...etc...you're both right and I'm always right even when I'm wrong, especially as I get so many things backwards first, being dyslexic LOL Have a Hoppy Chicken Day, Cheryl In Nome where its blowing like heck today

We ventilate to remove moisture, gases like ammonia and hydrogen sulfide, disease organisms, and heat. Ventilation air also replenishes oxygen consumed by gas brooders used to heat some poultry buildings. Under most conditions, we ventilate in the summer to remove heat and in the winter to remove moisture.

This one mentions controlling dust among other functions. However, it's a PDF and it won't let me cut and paste the text.

Anyway, it's starting to make sense to me.

Cheers,
Michelle

edited to add: I don't have a chicken in this fight, I'm just interested to know more about how to ensure proper ventilation. My quotes are not to bother anybody, just to provide some information that popped up.​

Thanks for the thoughts, Meesh.
My area usually has a couple of weeks (if we're lucky) of frosty cold during winter. It's hot during summer. I'm wondering if I really even need a coop for the hens. If an entire run is protected from predators, wouldn't a three sided shelter at one end, with roost/nest box work as well for chickens here?
The shelter would be sunny, especially during winter, and shaded during the hot summer. There would be plenty of ventilation, and they can keep themselves warm during the night.
With plants around the outside of the run, and a nice roost, I'm thinking the girls would be more comfortable than being enclosed during a hot night.
Hmmmmm.....